Alumina coated silicon carbide abrasive

Abstract

Disclosed is an improved abrasive material particularly useful as a dispersoid in metal matrices to provide articles of use having superior abrasive properties, especially at elevated temperatures. The improved abrasive material typically comprises silicon carbide particulate, the individual particles of which have a predominantly alumina coating thereon to inhibit dissolution of the particles in the metal matrix at high temperatures. The invention finds special application in abrasive blade tips for service in gas turbine engines, the tips comprising a nickel base or cobalt base superalloy having the alumina coated silicon carbide particles dispersed therein.

Having thus described typical embodiments of our invention, that which we claim as new and desire to secure by Letters Patent of the United States is: 
     
       1. A high temperature particulate, useful as an improved dispersoid in a metal matrix, comprising silicon carbide particulates having a predominantly alumina coating, the coating being resistive to diffusion or dissolution in superalloys at temperatures of 2000° F. or more. 
     
     
       2. A material for high temperature wear and rubbing resistance, comprising, a high temperature superalloy matrix having silicon carbide particles dispersed therein, the particles having a predominantly alumina coating, wherein the alumina coating is resistive to diffusion or dissolution in superalloys at temperatures of about 2000° F. 
     
     
       3. A material for high temperature wear and rubbing resistance comprising a high temperature superalloy matrix having silicon carbide particles dispersed therein, the particles having a first coating to improve bonding and a second coating of predominately alumina to resist diffusion or dissolution in superalloys at temperatures of about 2000° F., wherein the first coating is selected from the group consisting of silica and mullite. 
     
     
       4. A high temperature particulate material useful as an improved dispersoid in a metal matrix, comprising silicon carbide particulates having a first coating to improve bonding and a second coating of alumina to resist diffusion or dissolution in superalloys at temperatures of 2000° F. or more, wherein the first coating material is selected from the group consisting of silica and mullite. 
     
     
       5. The abrasive material of claim 1 wherein the thickness of the alumina coating is about 0.1 mil. 
     
     
       6. In the method for making a silicon carbide and metal matrix abrasive article useful at elevated temperatures, the improvement comprising, depositing an alumina coating on individual silicon carbide particles and dispersing the coated particles in a metal matrix, the alumina coating inhibiting diffusion of the particles into the matrix at elevated temperatures and increasing the useful life of the article. 
     
     
       7. The method of claim 6 wherein the coated particles are dispersed in the metal matrix by powder metallurgical techniques including mixing the coated particles with metal powder and then pressing the mixture into a consolidated body. 
     
     
       8. The method of improving the durability of high temperature silicon carbide particulate-containing metal which comprises coating the silicon carbide particulates, prior to inclusion within the metal, with at least one material selected from the group consisting of alumina, silica, mullite. 
     
     
       9. An abrasive blade tip for a gas turbine engine blade comprised of a superalloy having silicon carbide particulate of an average particle dimension of from 8 to 30 mils, the particulate having an alumina coating, the coating being resistive to diffusion into the superalloy at temperatures of about 2000° F. 
     
     
       10. A composite gas turbine blade made of a superalloy, having a tip according to claim 9.